Tuesday, October 07, 2008

Quarks: the source of protons and neutrons in atoms get recognition from the Nobel Commitee for Physics in 2008

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Particle physics celebrates Nobel

The protons and neutrons in atoms are made up of quarks The Nobel Prize in physics is to be shared by two Japanese citizens and an American, the Royal Swedish Academy of Sciences has announced.

Yoichiro Nambu, Makoto Kobayashi and Toshihide Maskawa provided new insights into the building blocks of matter.

Nambu described a mechanism called spontaneous broken symmetry in subatomic physics.

The work of Kobayashi and Maskawa predicted the existence of three families of particles known as quarks.

According to the Standard Model in particle physics - which ties together the smallest known building blocks of matter and three of nature's forces - quarks are the elementary sub-units of protons and neutrons, which together make up the nuclei of atoms.

The scientists' investigations explain anomalies that exist in the very fabric of the Universe.

According to the Nobel jury, "spontaneous broken symmetry is said to conceal nature's order under an apparently jumbled surface".

One analogy is to consider a pencil balancing on its point that then suddenly falls over. Prior to falling, the pencil is in perfect symmetry and has no preferred direction in which to topple; but in moving to the lower energy position of resting lengthways on the surface, the pencil suddenly defines a direction and the symmetry is broken.

What Nambu did was to formulate a mathematical description for this phenomenon in particle physics. The work is highly relevant in relation to upcoming experiments on the Large Hadron Collider (LHC), the recently completed giant accelerator at Cern on the Swiss-French border.

The LHC will search for an explanation for why the Universe has mass - with the leading candidate being the so-called Higgs field.

At the extremely high energies that existed in the very early Universe, symmetries would have existed that were then suddenly broken as the cosmos cooled and expanded. Theory suggests the mass resulted when the Higgs lost its symmetry.

Professor Sir Chris Llewellyn Smith, who was director general at Cern in the 1990s, said Nobel recognition for Nambu was long overdue.

"They play a key role in the unification of different forces in the successful Standard Model of particle physics."

The symmetries Nambu described are subtlety different to those studied by Kobayashi and Maskawa. Their work helps explain violations that occur in certain conservation laws at the particle level.

One key violation occurred immediately after the Big Bang, when just a small amount more matter than antimatter was created. Because these two kinds of particles annihilate each other when they meet, that excess of matter was responsible for seeding the Universe.

Kobayashi and Maskawa prevented a crisis in the Standard Model by showing the asymmetries could be accounted for if the numbers of recognised quarks was increased from three to six.

Observations subsequently confirmed their predictions.

Professor Nambu, 87, from the University of Chicago, is a US citizen but was born in Japan.

Professor Kobayashi, 64, works at the KEK Laboratory, Tsukuba, Japan; while Professor Toshihide Maskawa, 68, is affiliated to the University of Kyoto, Japan.